In 1901--just shy of the year 2000 being the company's hundredth anniversary--Illinois native Charles Walgreen opened his own drugstore after many years of working for other pharmacists and learning what they had and didn't have, and taking notes on customer service and other factors, all to figure out how to stand out. See, in the days before Walgreen's, drugstores were small, cramped, dimly-lit shops which sold drugs and medical supplies. That was it.
His longest employment was with Isaac Blood, with whom he learned so much that he one day grew confident enough to ask his boss if he could buy the store. Blood sold it to him...for $6,000.
Right away, Walgreen set to work. He installed bright lights and widened the aisles to make customers feel more welcome. He sold drugs that far exceeded the medicinal standards of the day. He and his associates personally greeted customers. He sold merchandise other than drugs so that his store became known around Chicago as "that one place you can go to when you need something right now and couldn't plan for because the need for it suddenly arose."
The store grew successful enough that it had grown to four outlets by 1916, by which time they had begun to look something like Mr. Gower's from It's A Wonderful Life--the soda fountain, the candy section. Needless to say, the company went from strength to strength, outlasting both the Great Depression and Charles Walgreen, Sr.'s passing in 1939.
The company got so successful that, in the 70s, it diversified into a chain of family restaurants, called Wag's, which stayed in business until 1991. I vaguely remember going to a Wag's at one point, back in........1991 or so; I believe it was over on 79th and Cicero, back when Goldblatt's had the department store there (it's now a Lowe's hardware superstore). All I remember is seeing the word "Wag's" on a pane of glass surrounded by some ferns, and recognizing the familiar Walgreen's font.
Anyway, here's the commemorative mug which Walgreen's sold when the three thousandth store opened.
Source: https://www.walgreens.com/topic/about/history/ourpast.jsp
